This invention relates to an electrical connector for circuit boards, and particularly to an edge connector having transmission line characteristics.
It is conventional for circuit boards carrying functional components of an electronic instrument to be connected together using a backplane circuit board. Generally, the functional circuit boards are disposed perpendicular to the backplane board, and conductor runs of the functional boards are connected to conductor runs of the backplane board by means of edge connectors which are carried by the backplane board. A conventional edge connector comprises resilient metal contacts which are secured to the backplane board and are in electrically-conductive relationship with conductor runs of the backplane board, and a contact positioner which is made of dielectric material and is held in position by mechanical arrangement with the metal contacts. The metal contacts are arranged in two rows. The contact positioner has two rows of teeth corresponding to the two rows of contacts, and the contacts and the corresponding teeth are in interdigitated relationship. The two rows of teeth are separated by a slot for receiving an edge region of the functional board. When the edge region of the functional board is received in the slot defined between the rows of teeth of the contact positioner, the metal contacts engage conductor runs of the functional board and establish electrically-conductive contact between the conductor runs of the functional board and the conductor runs of the backplane board. An arrangement of this kind may be used to connect a plug-in module to a mainframe or host instrument. When the plug-in module is inserted into the host instrument, a functional board of the plug-in module engages an edge connector on the backplane board of the host instrument and electrical connection is thereby established between functional components of the plug-in module and functional components of the host instrument.
A problem that arises in some instruments is that the tolerance on the position of the edge region of the functional board relative to the backplane board is quite large, and consequently the metal contacts must be quite long in order to ensure that electrical contact will reliably be made. In conventional edge connectors, the metal contacts do not have a transmission line configuration and therefore they do not have good high frequency performance.